A. Field of the Invention
The present invention relates to methods for enhancing the confidentiality of printed or typed messages. More particularly, the invention relates to a method and article for transmitting photocopies and telefax messages in a manner preventing a casual observer from reading messages contained in the documents.
B. Description of Background Art
Photocopying machines, perhaps as well as any other modern technological development, typifies that class of devices that causes many of us to "wonder how we ever did without them." Thus, many businesses, organizations and other enterprises, even small ones, possess one or more photocopying machines.
As is true of most every technological development, photocopying machines can be misused. Moreover, the use of photocopying machines can sometimes have effects not desired by the management of the organization or enterprise possessing the machine, for the following reasons.
In almost any organization, memos, letters or other documents are sometimes generated which contain sensitive information, which the author wishes be kept confidential. When copies of such sensitive documents are made on a photocopying machine, it would sometimes be desirable to prevent the contents of the document from being read by a casual observer. The present inventor is unaware of the existence of any simple prior art system which addresses the problem of making photocopied documents readily readable by an intended recipient, but unreadable by a casual observer.
Another office machine which is coming into widespread use at an even more rapid rate than the photocopying machine is the facsimile transmitting machine or "telefax." Telefax messages are most often transmitted from one location to a relatively remote location, whether that be a location across the street, across town, or half way around the world. Therefore, the sender of a telefax message frequently has little, if any, control over who might view the message.
Telefax machines optically scan an original document and produce a digital data stream corresponding to an image of the document. Thus, standard data encryption devices and methods may be used to transmit secure telefax messages. However, such devices and methods are generally complicated and costly.
In view of the considerations stated above, it would seem to be desirable to make available a simple, low cost method for making secure photocopies and telefax transmissions, secure being defined here as being unreadable by a casual observer. The present invention was conceived of in response to a perceived need for such a security system for photocopies and telefax messages.